Skipjack tuna is the English name. Japanese name is katuo. And scientific name is Katsuwonus pelamis. And there are seasonal Japanese namea, that for example is modorigatuo and kudarigatuo. The Skipjack tuna is designated as Kochi prefecture’s fish.
Skipjack tuna is eaten as tataki and sashimi in Kochi. And pole-and-line fishing of Skipjack tuna in Kochi is famous. And also raw Skipjack tuna in Kochi is very famous all over the country.
Skipjack tuna can grow to a body length of 1m of large size and to a body weight 18kg. Its form is spindle-shaped that has low hydrodynamic drag. Section is nearly ring shape.
Skipjack tuna belong to katuwonus of scombridae of scombroidei of perciformes of actinoptergii of vertebrate of chordate of animalia.
There are some varieties of scombridae; the striped bonito (Sarda orientalis), the Skipjack tuna (Katuwonus pelamis), the kawakawa (Euthynnus affinis).
Striped bonito is smaller than Skipjack tuna, but has a lot more of teeth than skipjack tuna, and also back color is different each other. Striped bonito’s color is blue, but Skipjack tuna’s color is deep indigo. The kawakawa, which range at over a large area of the tropical zone subtropical zone of the Indian Ocean, is heavier and has bigger withers weight than Skipjack tuna.
Skipjack tuna’s rage is the temperate zone and the tropical zone area of sea all over the world. ;It exists between the north latitude of 40° and the south latitude 40°of the equator’s both sides. Skipjack tuna visit each the Pacific Ocean side to the south of Hokkaido and Kyushu west coast at Japan. Skipjack tuna’ rage is very large, so discovery skipjack tuna’s migration course is very difficult.
As the above-mentioned, Skipjack tuna is living at temperate and tropical zone. This reason is that Skipjack tuna had a liking for water temperature 17~30°. Principally Skipjack tuna swim by school at sea surface of coast confine.
Skipjack tuna’s back body color is deep indigo and abdominal color is silver white of plain. This back and abdominal color is defense method to so-called counter shadowing. In that connection let me say that a lateral stripe come up to the abdominal when it is excited, and when it die , a vertical stripe and disappear a lateral stripe rise up to the abdominal.
Skipjack tuna is flesh-eating fish. They eat small size fish, crustaceans and cephalopoda. And they are migratory species of fish, so they move during the season, in other words, they goes up north in summer and go down south in autumn.
Usually Skipjack tuna swim at 25~50 kilometers an hour, and at times they swim about 100 kilometers an hour. But they die when they stop swimming. The reason is that skipjack tuna get a lot of oxygen from gills while they swim at high speed. So they experience oxygen shortage when they stop. Skipjack tuna stand higher rank of food chain, but t hey make large school so-called nagura, and play group action.
Skipjack tuna migrate along the Japan Current, so we can see at open sea of the Pacific Ocean (the Japan Current,) in early in summer to autumn in Kochi.